1. Field of the Invention
This invention relates broadly to the field of leak detection for high pressure containment systems. More specifically, this invention relates to an improved system and method for detecting steam leakage from boiler tubes and other areas of black liquor recovery boilers for the paper industry.
2. Description of the Prior Art
The economics of kraft pulping depend heavily on the safe, continuous operation of black liquor recovery boilers. In addition to their role in the regeneration of pulping chemicals, recovery boilers generate a large proportion of the steam required for mill wide operations. Despite the efforts of paper mills, insurance companies, and boiler manufactures, smelt-water expulsions caused by boiler tube leaks continue to pose a threat to normal boiler operations.
Methods to detect water leaks in recovery boilers have been proposed and tested by researchers for several years. Most leak detection schemes monitor the total airborne or structural acoustic energy levels within the boiler to determine if a leak is present. Many limitations of such acoustic leak detection strategies have been documented. Those limitations include the interference which is presented by high background noise levels, the attenuation of acoustic energy which takes place within the boiler, and the limited durability of acoustic sensors in the harsh environment of the boiler.
The most recent generation of acoustic leak detection systems, developed by Westvaco Corporation, utilizes spectral analysis techniques to overcome most of the inherent limitations of other acoustic leak detection schemes. This system is described in the July 1990 edition of the TAPPI Journal.
While the Westvaco system appears to be an improvement over previous generations of acoustic leak detection systems, it is still, to some extent, subject to the above identified disadvantages of acoustic leak detection technology. Moreover, all acoustic leak detection systems are expensive to purchase, deploy and maintain.
It should further be understood that improved detection accuracy is a characteristic which those involved in the design of leak detection systems are constantly striving to improve.
It is clear that there has existed a long and unfilled need in the industry for an improved leak detection system for black liquor recovery boilers which is less expensive, more accurate, and less suspectable to interference from background noise than commercially available acoustic leak detection systems are.